The aims of this application are 1. To isolate in pure form the chemotactic peptides form E. coli culture filtrates by means of HPLC and obtain their structure. 2. To isolate in pure form the chemotactic peptide of casein by HPLC, obtain the structure and test whether in reacts with the neutrophil formylpeptide chemotactic receptor. 3. To isolate and purify leukoegressin and test whether it reacts with the neutrophil formylpeptide chemotactic receptor. 4. To attempt to understand why the apparent affinity of competitive antagonists of the neutrophil formylpeptide chemotactic receptor varies with the nature of the formyl peptide agonist. These studies are designed to further explore the nature and reactivity of the chemotactic receptors of the neutrophil with respect to the mechanisms of the neutrophil functions in immune and non-immune inflammatory responses.